The present disclosure relates to a method for producing a V-ribbed belt.
When an uncrosslinked rubber composition containing short fibers is extrusion molded into an uncrosslinked rubber sheet, the short fibers are insufficiently oriented in the uncrosslinked rubber sheet. It is therefore difficult to produce a V-ribbed belt which is inexpensive, unlikely to generate a noise, and has a high wear resistance by using the uncrosslinked rubber sheet. For this reason, in practice, an uncrosslinked rubber sheet for forming V-shaped ribs in which short fibers are oriented in the width direction is prepared in the following manner. An uncrosslinked rubber composition containing the short fibers blended therein is kneaded, and then rolled with a calender to form an uncrosslinked rubber sheet in which the short fibers are oriented in the length direction. Subsequently, the uncrosslinked rubber sheet is cut perpendicularly to the length direction at regular intervals into rubber pieces. The rubber pieces are joined together at its sides, thereby forming the uncrosslinked rubber sheet. However, this method requires use of expensive short fibers, and the orientation of the short fibers must be precisely controlled.
To address this problem, as disclosed in, for example, Japanese Patent No. 5156881 directed to a production method of a V-ribbed belt, it has been known that an uncrosslinked rubber sheet for a compressed rubber layer is prepared by extrusion molding an uncrosslinked rubber composition which includes no short fibers but contains hollow particles and/or a foaming agent blended therein.